1. Field of the Invention
The present invention relates to a metal-coated white conductive fiber having a high degree of whiteness and superior conductivity, in which a metal coating provided on the fiber has superior adhesiveness. In particular, the present invention relates to a conductive fiber having a high degree of whiteness, comprising a metal coating having superior adhesion strength and conductivity provided on a fiber material composed of a polymer, such as a polyamide fiber or a polyester fiber. The conductive fibers of the present invention can be used as material for various cloths and clothing, and in addition, can be used in industrial materials, such as electromagnetic shielding materials, antistatic materials, and alternative materials for electrodes and electric cables.
2. Description of the Related Art
Conductive fibers are conventionally known in which metal thin-films are coated on the surfaces of fibers composed of polymer materials, such as polyamide fibers and polyester fibers, and in order to improve the adhesion of metal coatings thereto, various methods have been attempted. For example, in the case in which copper sulfide is coated, a method is disclosed in Japanese Examined Patent Application Publication No. 1-37513 in which a polymer material is pretreated with a dye having groups for binding copper ions so as to form bonds with copper ions and is then sulfurized, and a method is disclosed in Japanese Unexamined Patent Application Publication No. 6-298973 in which groups for binding copper ions are adhered to a fiber surface roughened by an alkaline treatment, and copper sulfide is then bonded thereto. In addition, in the case of materials which are difficult to plate with metal, such as aramid fibers, a method is disclosed in, for example, Japanese Translation of PCT International Publication for Patent Application No. 6-506267, in which metal ions are adhered to the fiber surface by using polyvinylpyrrolidone (PVP) and are then reduced so as to perform metal plating.
However, the plating method using PVP cannot be commonly used since it can only be applied to limited types of fibers. In addition, in the coating methods using the groups for binding copper ions, there are problems in that the metal coating obtained is only composed of copper or compounds thereof, and the adhesion strength of the metal coatings is not always sufficient. In this connection, adhesion strengths of metal coatings can be generally enhanced when fiber materials are roughened by alkaline treatment; however, when the degree of roughening of the surface and the conditions of the metal coating are not properly controlled, satisfactory effects cannot be obtained.
In addition, as a conventional method for manufacturing white conductive fiber, there are methods, for example, a method (a) for melt spinning a starting material for fiber compounded with a white conductive component, a method (b) for coating a white component on the surface of a fiber material containing a carbon component, which are disclosed in Japanese Unexamined Patent Application Publication Nos. 4-2808, 2-169715, 4-361613, and 60-126321, and a method (c) for coating a metal on fiber material by various methods, which are disclosed in Japanese Unexamined Patent Application Publication Nos. 7-179769 and 4-263667. However, the methods described above have the following problems as described below. That is, in the methods (a) and (b), the conductive fiber manufactured thereby has a volume resistivity of 105 to 106 xcexa9xc2x7cm or more, which is not sufficient conductivity for use in electromagnetic shielding, and hence, the conductive fiber thus formed can be applied only to antistatic applications and the like. In addition, in the method (c), pretreatment is performed using a dye prior to the metal coating in order to enhance the adhesion between the fiber and the metal to be coated, and due to the dye mentioned above, the original whiteness of the fiber material is degraded so that the coating has a slightly blue, green, gray, or black tone, whereby there are problems when they are used for textiles and for clothing.
In addition, a silver coated fiber used for conductive fillers and electromagnetic shielding materials is known which is formed by silver plating on an organic fiber; however, the longer fibers produced thereby are approximately 20 cm, and hence, the silver coated fiber cannot be commonly used since it is not a continuous fiber. In the case in which metal plating is performed on a continuous fiber in a state in which the fiber is wound around a shaft in the melt spinning step, when the continuous fiber in a wound state (wound fiber body) is metal plated by dipping in a plating solution, the plating solution may not sufficiently infiltrate inside the wound fiber body around which the continuous fiber is repeatedly wound, and almost all of the fibers are defective products having mottled plating, whereby it is difficult to obtain a continuous fiber in which the entire surface thereof is uniformly plated with metal.
The present invention solves the problems in the conventional white conductive fiber described above, and accordingly, an object of the present invention is to provide a white conductive fiber having a high degree of whiteness, and superior conductivity, and is to provide a manufacturing method therefor. The white conductive fiber described above has a metal coating uniformly coated on the entire surface thereof even though the fiber is a continuous fiber in a wound form. In addition, another object of the present invention is to provide a metal-coated conductive fiber having a metal coating thereon, in which the metal coating has superior adhesion strength and superior coating strength in addition to high conductivity. Furthermore, the present invention provides a method for manufacturing the conductive film described above and an apparatus therefor.
The present invention relates to a conductive fiber composed of a fiber material provided with a metal coating thereon having a degree of whiteness (L value in accordance with the Lab method) of 50 or more and a volume resistivity of 100 xcexa9xc2x7cm or less. In addition, the present invention relates to a conductive fiber composed of a fiber provided with a metal coating thereon, in which the surface of the metal coating has an orange peel texture.
The conductive fiber according to the present invention preferably has a degree of whiteness (L value) of 50 or more and a volume resistivity of 100 xcexa9xc2x7cm or less and has a metal coating thereon having an orange peel texture. As a fiber material, a polyester fiber, a polyamide fiber, or an acrylic fiber can be used. As a metal coating, silver, gold, platinum, copper, nickel, tin, zinc, palladium, or an alloy thereof may be used. The conductive fiber of the present invention more preferably has a degree of whiteness (L value) of 55 or more, a volume resistivity of 0.1 xcexa9xc2x7cm or less, and a metal coating provided with an orange peel surface having a surface roughness of 0.01 to 1 xcexcm.
Since the conductive fiber according to the present invention can be obtained in a continuous fiber form, the fiber is easily used for woven fabrics and the like and can be widely used for clothing materials and various fabric materials. In addition, since the fiber has superior conductivity, by weaving a small amount thereof with a base material, superior conductivity can be obtained without impairing the hue and the feeling of the base material. The conductive fiber can also be used for various conductive materials such as an electromagnetic shielding material. In addition, since the conductive fiber has beautiful whiteness, when spun with cloths or base materials provided with a hue having a high degree of whiteness, a product can be obtained without impairing the original colors thereof. Furthermore, since the conductive fiber can be formed of a commonly used continuous fiber, such as a polyamide fiber, a polyester fiber, and an acrylic fiber, the conductive fiber can be used for broader applications.
Since the metal coating provided on the conductive fiber according to the present invention has an orange peel surface, the metal coating has superior adhesion, and more particularly, has a standard strength of grade 3 or more. In addition, when a metal coating is formed of silver having silver ions with antifungal properties, the conductive fiber having the metal coating thereon can be used as an antifungal material. Furthermore, when surface treatment is further performed on the metal coating provided on the fiber, such as anticorrosion treatment and oiling treatment, degradation of the whiteness and decrease in the adhesion can be avoided, and the slipping properties of the fiber can be improved by oiling treatment.
The conductive fiber according to the present invention can be preferably used for a woven fabric, a non-woven fabric, a knitted fabric, a clothing material having antifungal properties, an electromagnetic shielding material, an antistatic material, an alternative material for an electrode and an electric cable, and a conductive reinforcing material for a fiber-reinforced plastic.
The present invention relates to a method for manufacturing a conductive fiber comprising the steps of providing a tubular fixing shaft having a plurality of holes for passing a solution in a plating bath, mounting a wound fiber body formed by winding a fiber material around a core to the fixing shaft, forming a flow path of a plating solution from the fixing shaft to the plating bath via the wound fiber material so as to infiltrate the plating solution into the wound fiber body, and performing electroless plating on the fiber material while the plating solution flows. The method for manufacturing a conductive fiber described above preferably further comprises a step of temporarily forming a flow path of the plating solution from the plating bath to the fixing shaft via the wound fiber body so as to infiltrate the plating solution into the wound fiber body.
As described above, the manufacturing method described above comprises the step of forming the flow path of the plating solution from the fixing shaft to the plating bath via the wound fiber body so as to infiltrate the plating solution into the wound fiber body. When the flow path is formed from the fixing shaft to the plating bath via the wound fiber body, the wound fiber body is expanded toward the outside, and the plating solution infiltrates into the gaps in the wound fiber body formed by winding a continuous fiber, whereby plating can be performed uniformly on the entire surface of the fiber.
In addition to the step of forming a flow path from the fixing shaft to the plating bath via the wound fiber body, the method for manufacturing a conductive fiber of the present invention may further comprise the step of temporarily forming a flow path from the plating bath to the fixing shaft via the wound fiber material so as to infiltrate the plating solution into the wound fiber body. When the flow path is temporarily formed from the plating bath to the fixing shaft via the wound fiber body so as to infiltrate the plating solution received in the plating bath into the wound fiber body by stopping the flow path from the fixing shaft to the plating bath via the wound fiber body, plating can be performed more uniformly.
The manufacturing method described above preferably further comprises, after the step of mounting the wound fiber material, a step of washing treatment, a step of alkaline treatment, a step of neutralization treatment, and a step of activation treatment, in which the subsequent step of performing electroless plating is one of a step of performing silver electroless plating and a step of platinum electroless plating. Accordingly, metal plating is performed uniformly on the entire surface of the continuous fiber even though in a wound body, whereby a white conductive fiber can be manufactured having a degree of whiteness (L value) of 50 or more, and more preferably, of 55 or more, and a volume resistivity of 100 xcexa9xc2x7cm or less, and more preferably, of 0.1 xcexa9xc2x7cm or less.
The present invention relates to an apparatus for manufacturing a conductive fiber comprising a plating bath, a detachable fixing shaft mounted in the plating bath, a storage tank for storing a plating solution, a first solution supply tube communicating between the plating bath and the storage tank, and a solution supply pump provided to the first solution supply tube. In the apparatus according to the present-invention, the fixing tube is formed of a hollow cylinder and is provided with a plurality of holes for passing solution in the wall thereof, the first solution supply tube is connected to the fixing tube, and the plating solution is supplied to the plating bath via the fixing shaft. The apparatus preferably further comprises a second solution supply tube for discharging the plating solution from the plating bath to the storage tank, wherein the first solution supply tube and the second solution supply tube form a circulating path for circulating the plating solution. According to the manufacturing apparatus described above, the manufacturing method described above can be easily carried out.
According to the present invention, a white conductive fiber, which is a continuous fiber wound around a core, can be obtained having high conductivity preferably used for electromagnetic shielding. The white conductive fiber has a volume resistivity of 100 xcexa9xc2x7cm or less, and more preferably, of 0.1 xcexa9xc2x7cm or less, and has a degree of whiteness of 50 or more, and preferably, of 55 or more. Since the conductive fiber according to the present invention has beautiful whiteness, when spun with cloths or base materials provided with a hue having a high degree of whiteness, a product can be obtained without impairing the original colors thereof. Since the fiber has superior conductivity, by weaving a small amount thereof with a base material, superior conductivity can also be obtained without impairing the hue and the feeling of the base material. In addition, since pretreatment and plating can be performed for a fiber in a cheese winding form, a conductive fiber having high performances can be obtained at an inexpensive cost. Furthermore, since the conductive fiber can be formed of a commonly used continuous fiber, such as a polyamide fiber, a polyester fiber, and an acrylic fiber, the conductive fiber can be used for broader applications. Since the metal-coated fiber of the present invention comprises a metal coating provided thereon having high adhesion, the durability thereof is significant, and the superior conductivity can be maintained over long periods of time, whereby the metal-coated fiber is preferably used for various conductive materials. In addition, since the metal coating formed by silver plating has superior antifungal properties due to the silver ions in the metal coating, the conductive fiber of the present invention may be used as antifungal materials.